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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 240

post #3586 of 10501

Excellent Day!   My Voshkod 6ZH1P - EV tubes arrived from Yen this morning via the USPS regular Saturday mail delivery.  I need to spend some time having them burn-in a bit with the Little Dot I+ through the day, and will look forward to a late evening session of checking out the various passages in my music to see how they fare.

post #3587 of 10501
Quote:
Originally Posted by Audiofanboy View Post
 

 

Funny, I thought about trying the same trick with 6N30P-DR tubes, but ended up not because mu would be a little on the low side for driver tubes, and gm would be over the roof (it's already quite high with 6DJ8 tubes)!

 

How does it sound though, good?

6N6P-IR and 6N6P-i sounds good. Chinese 6N6 has weird rough electric kind sound with some distortion. I think this is good way to test which powertube sounds good. Problems with sound multiply.

;-)

post #3588 of 10501
Quote:
Originally Posted by Artsi View Post
 

I made new THE PRO BOX adapter. I bought made in Canada electric box for it. I took some photos how to make such a thing. This box could be opened afterwards since it is assembled together with 4 screws.

 

 

700

I made holes to bottom of the box. Paper is there protecting little dot from getting any epoxy. You just push pins through paper. I glued parts together with epoxy.

 

Edit: Box type is 1591MSBK from hammond manufacturing.

 

GREAT JOB!!

 

THANK YOU!! :)

 

Since I have never worked with plastic before.... What kind of tool do you use to cut the holes?

post #3589 of 10501
Quote:
Originally Posted by gibosi View Post
 

 

GREAT JOB!!

 

THANK YOU!! :)

 

Since I have never worked with plastic before.... What kind of tool do you use to cut the holes?

I drilled 10mm hole and grinded it bigger. Even with knife it is possible to slowly make such hole. This is possibly the best option http://www.sahkonumerot.fi/6421771/img/large/color.jpg.

post #3590 of 10501
Quote:
Originally Posted by gibosi View Post
 

 

GREAT JOB!!

 

THANK YOU!! :)

 

Since I have never worked with plastic before.... What kind of tool do you use to cut the holes?

you use this with a drill makes nice round hole if you can get the right size.

post #3591 of 10501
Quote:
Originally Posted by Artsi View Post
 

I made new THE PRO BOX adapter. I bought made in Canada electric box for it. I took some photos how to make such a thing. This box could be opened afterwards since it is assembled together with 4 screws.

700

Here are the most of things you need to make it. 1mm (18gauge) thick copperwire for the pins is covered with lacquer, so it need to be removed first by grinding.

700

Here are the parts for the pins. B7G socket is just to keep pins more straight when gel super glueing pins through pin protector/straightener. I grind wire head more round.

400

Here it is waiting drying.

700

I made holes to bottom of the box. Paper is there protecting little dot from getting any epoxy. You just push pins through paper. I glued parts together with epoxy.

700

This show the extra wires for the switch.

700

And how the switch is connected to the B9A socket.

700

Soldered all rest wires. Cutted those additional copper wires shorter after taking photo.

700

And here is ready to use product.

 

Sharp-eyed can see that i connected heating from both channels. I measured that they are connected anyway inside little dot. So i think with double wiring i can use up to 0.9A heater current.

 

First wooden box with crappy tube bottoms had very little humming in the right channel with ecc83 tube. It was so little that needed completely silence to notice. Now all humming is gone. I think that there is no need for any kind grounding to pin9 for 6V tubes. Stereo imaging and channel separation is excellent for my hearing.

 

Enjoy! :-)

 

Edit: Box type is 1591MSBK from hammond manufacturing.

Looks great very nice Artsi nice picture . About the connections i have a picture for you , could you link the different sockets with crayon so we can see what wire to solder where when you have a chance .Just make shure i numbered the socket hole correctly first. Thanks a bunch .

 


Edited by MIKELAP - 10/19/13 at 11:02am
post #3592 of 10501
Quote:
Originally Posted by MIKELAP View Post
 

you use this with a drill makes nice round hole if you can get the right size.

 

 

Quote:
Originally Posted by Artsi View Post
 

I drilled 10mm hole and grinded it bigger. Even with knife it is possible to slowly make such hole. This is possibly the best option http://www.sahkonumerot.fi/6421771/img/large/color.jpg.

 

Thanks guys! Now I know what I am looking for. :)

post #3593 of 10501
Quote:
Originally Posted by MIKELAP View Post
 

Looks great very nice Artsi nice picture . About the connections i have a picture for you , could you link the different sockets with crayon so we can see what wire to solder where when you have a chance .Just make shure i numbered the socket hole correctly first. Thanks a bunch .

B9A numering is wrong. Looking from like bottom of the tube numbering goes clockwise. Switch could be ON-ON type, but has only 6 pins. ON-ON switch with 9 pins works. I need go to sauna...

post #3594 of 10501

   Would this be better .Thanks

post #3595 of 10501

1000

 

hope this helps a little.


Edited by Artsi - 10/21/13 at 11:32am
post #3596 of 10501
Quote:
Originally Posted by Artsi View Post
 

1000

hope this helps a little.

Thanks a lot .

post #3597 of 10501
LOL! You two are ingenious!
Bravo!
post #3598 of 10501

Artsi...

 

Sorry but I have a bit of a problem with bridging the heater pins on the B7G sockets together...

 

Here is the label off the transformer in my MK IV.

Wire Translation:

 

The driver filament winding is the 3.3 V * 2/1A so I personally wouldn't use a tube that has a 0.9A draw...

The wire designation of the 3.3 is Green / Black / Green which tells me it's a 3.3V center tap.

The power filament winding is the 6.8V/2.5A on the White / White.

AC to the on board bridge is the 175/0.1A Yellow / Yellow wires.

 

Is the transformer on your MK II the same?

 

It is possible that on the above transformer they have the 2 x 3.3V windings in series to get 6.6v and are sending one set to each tube.

I really don't want to unbolt the my transformer from the chassis to check how they are dealing with these center taps and 3.3V winding wires.

 

Paralleling the windings can be a problem sometimes.

Quote:  Rod Elliott (ESP)
 Parallel connection of transformer windings is permitted in one case only - the windings must have exactly the same voltage output, and must be connected in phase. Different current capacities are not a problem, but it is rare to find a transformer with two windings of the same voltage but different current ratings.

Even a 1V difference between winding voltages will cause big problems. A typical winding resistance for a 5A winding might be 0.25 ohm. Should two such windings be connected in parallel, having a voltage difference of 1V, there will be a circulating current limited only by the resistances of the windings. For our example, the total winding resistance is 0.5 ohm, so a circulating current of 2A will flow between the windings, and this is completely wasted power. The transformer will get unexpectedly hot, and the maximum current available is reduced by the value of the circulating current.

Should the windings be connected out of phase, the circulating current will be possibly 100A or more, until the transformer melts or the fuse blows. The latter is generally to be preferred.

The transformer manufacturer's specifications will indicate if parallel operation is permitted. If you are unsure, measure the voltages carefully, and avoid parallel connection if the voltages differ by more than a couple of hundred millivolts. There will always be a difference, and only the manufacturer's winding tolerances can predict what it will be. With toroidal transformers, the windings are often bifilar, meaning that the two windings are wound onto the transformer core simultaneously. The tolerance of such windings is normally very good, and should cause no problems.


Can you see if you have the same label on your transformer, you just have to take the top cover off and it should be right there.

 

Thanks!

:beerchug:

post #3599 of 10501
Quote:
Originally Posted by TrollDragon View Post
 

Artsi...

 

Sorry but I have a bit of a problem with bridging the heater pins on the B7G sockets together...

 

Have you measured resistance between channels pins 3 and 4? With my MK II resistances are about 0.1ohms. Transformer cover is too complicated to take apart.

 

The most reliable way to do the adapter is to use heater wiring only from one channel.


Edited by Artsi - 10/20/13 at 2:35am
post #3600 of 10501

Alright! I managed to find a single, super strong (as in 20% over NOS) Amperex "Orange Globe" 6DJ8 from the late 60s (so not a "Bugle Boys" 6DJ8 from the early or mid-60s, and not an "Orange Globe" with an A-frame getter from 70 onwards), so the best Amp'ex short of some crazy rare tubes, recommended by all who have tried them. I just communicated with a seller who was selling some very nice pairs for "OK" prices, asked him if he had singles, and obviously he had plenty and was willing to sell them for less than half of the price of a pair (cheaper than buying pairs, which is a bit ironic).

 

Keeping up on my strategy of just going for it and getting the best -instead of spending the same money on more tubes I'll never use- I got the best I could, basically. But even then, I don't find the prices that shocking really, compared to the 3 digit legends I see over on the Lyr thread (I ended up paying $42 for the tube, shipping to France included, and that's $10 right there; seller would have shipped for $37 to the US, which really isn't horrible for super strong premium tubes). Again, I think the "pair effect" really ramps up the prices, and sellers are just dying to sell single tubes they don't have a match for!

 

About heater wiring to adapt a single tube instead of two, it does feel more natural and "safe" to just use the 6V heater pins on one side and just be done with it. Besides, it's also easier!

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